In addition to a housing, semiconductor modules may include a metallized substrate (e.g., made of ceramic), to which semiconductor chips are attached, and electrical terminals, by which the semiconductor module or its chips can be electrically connected to additional components. These electrical terminals, which are generally produced from copper, may, for example, be connected to the metal layer of the substrate by means of ultrasonic welding.
During the ultrasonic welding of copper terminals to the substrate, particles may be produced that may lead to difficulties if they remain at critical points within the module, such as contacts of the semiconductor chips or on the insulating ceramic, for example.
Since these particles tend to stay attached to polymeric materials, such as polyimides, for example, it may be difficult to remove the particles from the module after the welding operation.
It is possible to enclose the particles in the region around the foot of the terminal by a suitable housing, but the metalized terminal welding point would have to be designed to be very large for this to allow an enclosing structure to be placed on it.
If the enclosing structure were placed onto the insulating ceramic, it could reduce its insulating effect. Furthermore, it may be that a moving plastic part tears away the surrounding silicone gel from the metal and from the ceramic, which could impair the insulation.
WO 2014 000 975 A1 describes, for example, a method for ultrasonically welding terminal elements to a substrate for electronic components in which the welding point is enclosed during the welding operation by a structure that is intended to prevent particles that may be produced during the welding operation from contaminating the substrate.
JP 2010 040 615 A2 proposes to prevent particles produced during ultrasonic welding from contaminating a semiconductor device. For this purpose, a plastic is applied around the welding point.
It has also been proposed to carry out the ultrasonic welding within a foam, it then being possible for the particles produced to be washed away together with the foam after the welding. This generally leads, to a cost-intensive production process.
U.S. Pat. No. 4,970,618 describes a computer disk with a housing that is ultrasonically welded and has portions which control an air flow when the magnetic disk rotates, in order to prevent that particles produced during the ultrasonic welding can reach the disk.